Microfluidic devices have been widely used in biomedical, biochemical and trace analysis, etc. On the great demand of the reliability for bioanalytical devices, disposable cartridges or chips are more and more welcomed as the carrier for reaction and detection. Sometimes fluid is injected into the cartridge or chip manually but this will result in low reliability. On the other hand, a micropump is often not easy and too expensive to be integrated into the disposable part.
Many kinds of micropumps have been studied in the recent years. Unlike conventional peristaltic pumps which commonly comprise a flexible tube and three or more rollers (See e.g., U.S. Pat. Nos. 6,062,829 and 6,102,678, and European Patent Nos. 1,078,879 and 1,099,154), micro pumps generally consist of three or more chambers among which fluid is transferred from one to another (See e.g., U.S. Pat. Nos. 5,085,562 and 5,759,015, and WO01/28,682). For example, in WO01/28,682, three identical chambers are connected in tandem and driven independently by three drives in a peristaltic time sequence and then fluid is transferred.